A prefect at Hogwarts School of Witchcraft and Wizardry is a student who has been given extra authority and responsibilities by the Head of House or Headmaster or headmistress. One male and one female student are chosen from each house in their fifth year to act as prefects, and would continue to be prefects in their sixth and seventh years until they leave school. Thus, there are approximately six prefects per house, and twenty-four prefects in the whole school at one time. The Head Boy and Head Girl may be chosen from among this number and may not be replaced, but, like with James Potter, the Head Boy or Girl does not have to be a prefect.

The Weasley family is noted for having had several prefects among its sons - first Bill, next is Charlie, then Percy and finally Ronald Weasley. Percy in particular is known to have been mercilessly persecuted by his brothers Fred and George, who once bewitched his Prefect's badge to read "Pinhead", and were once quoted by Ron as having "always said that only prats become Prefects".

Prefects are allowed to take House points away from other students in their own house as a penalty for rule-breaking, but they are not allowed to take points from other prefects or students in other houses. Prefects can give detentions as a form of punishment.

Prefects patrol the corridors of the Hogwarts Express on the way to school and attend a meeting in a special prefects' carriage where they are instructed by the Head Boy and Girl. They also patrol hallways to ensure that other students are not breaking curfew. There is a bathroom with a large, pool-like bath on the fifth floor of Hogwarts Castle that is reserved for prefects and Quidditch captains. It is located at the fifth door to the left of the statue of Boris the Bewildered. The only known password to this bathroom is "pine fresh", which was used during the 1994–1995 school year.

Prefects have other responsibilities as student leaders. They show the first years the way to their dormitories on their first day of school at Hogwarts School of Witchcraft and Wizardry, and supervise the decorating of the castle for Christmas (and presumably other events as well). They also watch the younger students when bad weather keeps them indoors over break times.[1]

Percy Weasley when he was a prefect in 1991

Once a student becomes a prefect, they have a better chance of becoming Head Boy or Head Girl; however, a student is not required to earn the former honour in order to earn the latter. This fact was exemplified in the knowledge that Remus Lupin was a Gryffindor prefect but James Potter was later appointed the Head Boy.

Prefects are given a badge; the colours are the colours of the prefect's House and/or silver[2]. They are supposed to wear the badge on their school uniform. The badge would have the letter "P" on it while the Head Boy's badge would have "Head Boy" on it, and the Head Girl's with "Head Girl". If the prefect is on his or her house Quidditch team, he or she would not be required to wear the prefect badge on their Quidditch robes.

Ron Weasley's prefect badge

Hermione Granger was a sensible prefect, and took the role very seriously. Ron Weasley was a little less serious about it, to the point of neglecting several rules. In fact, he was extremely surprised to be chosen as a prefect as he expected Professor Dumbledore would have chosen Harry. Dumbledore thought Harry would have too much on his mind and gave it to Ron instead. Ron received a letter from his brother Percy, stating that Ron might risk losing his badge by associating with the apparently dangerous Harry Potter. This may mean if the prefects cross a certain point of abusing their powers, they might have their position revoked.

Draco Malfoy and Pansy Parkinson abused their positions greatly, to the annoyance of Hermione Granger, by being uncharacteristically harsh towards first years and deducting points from students who do not strike their favour. In his sixth year, Draco refused to live up to his prefect duties any further, in preference of his Death Eater mission of assassinatingAlbus Dumbledore. This could mean that students have the right to reject the position of prefect any time they desire, or that Draco was punished for rejecting his obligations.

It is also unclear as to who has the power to appoint a Prefect, the Head of House or Headmaster. Dumbledore had stated in the fifth book that he did not want to make Harry a Prefect because he felt he had too much already on his his mind. Yet Draco Malfoy and Pansy Parkinson abuse their position greatly and were biased towards their own house. Possibility in their appointment may be influence or recommendation made by Severus Snape, who favoured Slytherins due to them being in his house, or the two were simply the least biased and most suitable when compared to the rest.